Rubber compounding



Patented Jan. 26, 1937 UNITED STATES ATENT OFICE RUBBER COMPOUNDING NDrawing.

Application November 14, 1935,

Serial No. 49,737

4 Claims.

My invention relates to improvements in the manufacture of vulcanizedrubber products. In one aspect, my invention relates to the developmentof improved fatigue resistance in vulcanized rubber products. In thisaspect, my present invention is an improvement on the broader inventiondescribed and claimed in my application filed December 5, 1934, SerialNumber 756,075.

I have discovered that, by using a hydroxyquinol, and particularly1,2,4-trihydroxybenzene, and an organic base such as an ethanolamine inconjunction with catalytic antioxidants such as phenylbetanaphthylamine,I can produce vulcanized rubber products in which both resistance toaging and resistance to fatigue are developed to a high degree. In thisaspect, the process of my invention comprises, essentially, thevulcanization of a rubber compound including 1,2, i-trihydroxybenzene,an organic base and a catalytic anti-oxidant and the product of myinvention comprises, essentially, the product of such vulcanization. Thedifferences between resistance to aging and resistance to fatigue, asproperties of vulcanized rubber compounds, and the problems involved indeveloping these properties jointly in the same vulcanized rubbercompound are outlined in my prior application, above identified, and forthat reason are not repeated here.

1,2,4-trihydroxybenzene is sometimes designated, although lessprecisely, by other terms such as hydroxyhydroquinone, oxyhydroquinoneand oxyquinol. 1,2,4-trihydroxybenzene is correctly designated as anhydroxyquinol.

Hydroxyquinols, and particularly 1,2,4-trihydroxybenzene may be used asa substitute for any of the oxygen absorbers specifically mentioned inmy said prior application in the processes and in the production of theproducts there described. I have found 1,2,itrihydroxybenzene to be moreactive as an oxygen absorber, for the purposes of my invention, thanhydroquinone, to be substantially as active as pyrogallol and in generalto enjoy the advantages, for the purposes of my invention, of mixturesof pyrogallol and hydroquinone.

The organic bases useful for the purposes of my invention are thosenon-volatile at the vulcanization temperature, miscible with rubber andeffective to activate the hydroxyquinol as an oxygen absorber. Suchorganic bases include monoethanolamine, diethanolamine, triethanolamlne,dibutylamine, tributylamine, diamylamine, dibenzylamine and aniline. Thecatalytic antioxidants useful for the purposes of my invention are thoseefliective to inhibit oxidation of the 5 vulcanized rubber product bythe oxygen content of the atmosphere to which it may be exposed Suchcatalytic anti-oxidants include the aromatic secondary amines, or thereaction products of aromatic amines with aldehydes or the reactionproducts of aromatic amines with ketones, more particularly,diphenylamine, the ditolylamines, phenylalphanaphthylamine,phenylbetanaphthylamine, diphenylparaphenylenediamine,dibetanaphthylparaphenylenediamine, the reaction product of acetaldolwith alphanaphthylamine, the reaction product of diphenylamine withacetone and the reaction products of acetone with aniline.

My invention will be further illustrated by the following examplesincluding processes embodying my invention, processes producing productsembodying my invention. The examples designated by number illustrate myinvention. The examples designated by letter are given for purposes ofcomparison.

The following Compounds A to F inclusive and 1 to 12 inclusive werecompounded in the usual manner, the hydroxyquinol, in Compounds 1 to 12,being incorporated as such or as a mixture with the organic base afterincorporation of the other compounding materials.

Compound A consisted of:

Parts (by weight) Smoked sheets 100 Stearic acid 4 Pine tar 2 Zinc oxide5 Carbon black 4 Sulfur 3 Mercaptobenzothiazole (accelerator) 1 CompoundB was the same as compound A ex cept for the inclusion of 1 part ofphenylbeta naphthylamine (antioxidant). Compound C 45 consisted of:

Parts (by weight) Smoked sheets 100 Soft carbon black 40 Zinc oxide 10Parts (by weight) Stearic acid l Parafiin 0.5 Phenylbetanaphthylamine 1Aldolalphanaphthylamine reaction products (anti-oxidant) 1 Sulfur 0.6Mercaptobenzothiazole accelerator) 1.5 Tetramethylthiuramdisulfide do0.25

Compound D consisted of:

Parts (by weight) Smoked sheets 100 Calcium carbonate coated with 3% (byweight) of stearic acid Zinc oxide 10 Red oxide of iron (color pigment)2.5 Stearic acid 0.5 Parafiin 0.5

Phenylbetanaphthylamine (anti-oin'dant) 1 Aldolalphanaphthylaminereaction prodducts (anti-oxidant) 1 Sulfur 0.75 Mercaptcbenzothiazole(accelerator) 0.75 Tetramethylthiuramdisulfide (accelerator) 0.15Tellurium 0.5 Benzothiazyldisulfide- (accelerator) 0.75

Compound E was the same as Compound A except for substitution of 1 partof benzothiazyldisulfide for the mercaptobenzothiazole, and Compound Fwas the same as Compound B except for the substitution of 1 part ofbenzothiazyldisulfide for the mercaptobenzothiazole.

Compounds 1, 2, 3, and 4 were the same as Compound 13 except for theinclusion of 0.75 parts of 1,2,4-trihydroxybenzene in Compound 1, of0.75 parts of 1,2,4-trihydroxybenzene and 0.25 parts of monoethanolaminein Compound 2, of 0.5 parts of 1,2,4-trihydroxybenzene in Compound 3,and of 0.5 parts of 1,2,4-trihydroxybenzene and 0.25 parts ofmonoethanolamine in Compound 4. Compounds 5 and 6 were the same,respectively, as Compound F except for the inclusion of 0.75 parts of1,2,4-trihydroxybenzene in Compound 5, and of 0.7 parts of1,2,4-trihydroxybenzene and 0.25 parts of monoethanolamine in Compound6. In another aspect, Compounds 5 and 6 were the same, respectively, asCompounds 1 and 2 except for the substitution of 1 part ofbenzothiazyldisulfide for the mercaptobenzothiazole. Compounds 7 and 8were the same as Compound A except for the inclusion of 0.5 parts of1,2, i-trihydroxybenzenc in Compound 7, and of 0.5 parts of1,2,l-trihydroxybenzene and 0.25 parts of monoethanolamine in Compound8. Compounds 9 and 10 were the same as Compound E except for theinclusion of 0.75 parts of 1,2,e-trihydroxybenzene in Compound 9, and of0.75 parts of 1,2,4=-trihydroxybenzene and 0.25 parts ofmonoethanolamine in Compound 10. Compounds 11 and 12 were the same,respectively, as Compounds C and D except for the inclusion in each of 1part of 1,2,4-trihydroxybenzene and 0.5 parts of monoethanolamine.

The seven test slabs, samples, and test pieces, samples, for determiningresistance to fatigue in flexure as hereinafter described werevulcanized in a platen press at 135 C. or 153 C. for periods varyingfrom 4 minutes to 120 minutes. Samples of Compounds, A, B, E, and F and1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 were vulcanized at 135 C. for 30minutes, minutes, minutes and 120 minutes. Samples of Compounds C and Dand 11 and 12 were vulcanized at 153 C. for 4 minutes, 8 minutes and 16minutes.

In the following tabulations, values for physical properties for eachcompound are in the order of increasing periods of vulcanization. Inthese tabulations, the values for stress at 300% elongation, in poundsper square inch, appear under the caption (a), for tensile strength, inpounds per square inch, under the caption (b), and for the percentageelongation at break under the caption (0), and the values for fatigueresistance, determined as hereinafter described, after 50,000 completecycles of fiexure, after 100,000 cycles, after 150,000 cycles and after200,000 cycles appear under the captions (7), (is), (Z), and (m),respectively. Also in these tabulations, the same values after 4 days ofaccelerated aging in the oxygen bomb appear under the captions (aa),(bb), (cc), (77'), (klc), (2!), and (mm), respectively.

Fatigue resistance is conveniently measured in the DeMattia fatiguetesting machine in accordance with conventional practice. For thepurpose of measuring resistance to flex cracking on flexme, the test isconveniently carried out as follows, and the comparisons herein madewith respect to flex cracking are based upon tests so carried out: Testpieces are molded as rectangular blocks. 6 x l" x with an indentationtransversely across one fiat side of the piece at its center produced bythe insertion into the mold, of a half round steel bar of 3 g" radius.With the slides of the testing machine positioned 4 inches apart atmaximum separation, the test pieces are clamped between them unstressed.The test pieces are then flexed, so as to stress the indented side ofthe test piece under tension, by operation of the testing machine. Thetest pieces, bent double through the indentation to expose the surfaceof the indentation, are periodically graded against a series of elevensamples, similarly bent, showing progressively deterioration from noflex cracks to complete rupture and marked in the same order 0, 1, 2, 3,4, 5, 6, 7, 9, 10. A test piece corresponding to the first standard ismarked 0, the one corresponding to the fourth is marked 3, and so on. Inthe examples herein, the figures on fatigue resistance are given thegrading of individual samples and as the summation of the gradings of 3or 4 samples, the grading 10, 30 or 40, respectively, thus indicatingcomplete rupture of the test piece or of all three or four test piecesand progressively lower gradings Compound B Summation (4 tests) 1 11 1826 Summation (4 tests)" 12 21 28 33 Compound C Summation (3 tests) 4 1521 Compound D Summation (3 tests) 8 25 29 Compound E Summation (4 tests)4 16% 23 36 Summation (4 tests) 29 39 40 40 Compound F Summation (4tests) 0 3% 8% 13 (W (if) Summation (4 tests). 15% 21% 25 32 Compound 1Summation (4 tests)- 2 9 13 19 Summation (4 tests) 8 14 21 26 Compound 2Summation (4 tests)" 1 6 9 13 (a M) 1') (ii) (ll) Summation (4 tests) 511 22 27 Compound 3 Summation (4 tests) 3 8 13 21 Compound 4 Summation(4 tests) 2 5 10 18 Compound 5 Summation (4 13513)." 0 0 4% 7 (111 WI)(ii) (k Summation (4 tests) 5% 13 19 30 Compound 6 Summation (4 tests) 01 5% 8 Summation (4 tests) 4% 11% 20 28 Compound 7 Summation (4 tests)"8 22 40 40 Compound 8 Summation (4 tests) 9 23 37 40 Compound 9Summation (4 tests) 1 7 15 26 Summation (4 tests)" 30 39 40 40 Compound10 Summation (4 tests). 1 5% 17% 28 Summation (4 tests). 31 39 40 40Compound 11 Summation (3 tests) 0 COD 0: Hon

Compound 12 Summation (3 tests) Although, in practicing the process ofmy invention, the rubber compounds, as compounded, are normally dry, thecatalytic anti-oxidants and the hydroquinol being incorporated as such,the compounding is carried out in the usual manner, with no specialprecautions to exclude moisture, from the atmosphere for example, makingit probable that moisture is present to the extent in which it isusually encountered, in amounts of the order of 0.5% by weight of thecompound for example.

I claim:

1. In the manufacture of vulcanized rubber products, the improvementwhich comprises sub .iecting to vulcanization a rubber compoundincluding a hydroxyquinol, an organic base nonvolatile at thevulcanization temperature and miscible with rubber efiective to activatethe hydroxyquinol as an oxygen absorber and a catalytic anti-oxidant.

2. In the manufacture of vulcanized rubber products, the improvementwhich comprises subjecting to vulcanization a rubber compound including1,2,4-trihydroxybenzene, an organic base nonvolatile at thevulcanization temperature and miscible with rubber effective to activatethe hydroxyquinol as an oxygen absorber and a catalytic anti-oxidant.

3. The product of vulcanization of a rubber compound including ahydroxyquinol, an organic base nonvolatile at the vulcanizationtemperature and miscible with rubber efiective to activate thehydroxyquinol as an oxygen absorber and a catalytic anti-oxidant.

4. The product of vulcanization of a rubber compound including1,2,4-trihydroxybenzene, an organic base nonvolatile at thevulcanization temperature and miscible with rubber efiective to activatethe hydroxyquinol as an oxygen absorber and a catalytic anti-oxidant.

ALBERT A. SOMERV'ILLE.

